.\"	$OpenBSD: enc.4,v 1.22 2006/05/26 08:51:29 jmc Exp $
.\"
.\" Copyright (c) 1999 Angelos D. Keromytis
.\" All rights reserved.
.\"
.\" Redistribution and use in source and binary forms, with or without
.\" modification, are permitted provided that the following conditions
.\" are met:
.\"
.\" 1. Redistributions of source code must retain the above copyright
.\"    notice, this list of conditions and the following disclaimer.
.\" 2. Redistributions in binary form must reproduce the above copyright
.\"    notice, this list of conditions and the following disclaimer in the
.\"    documentation and/or other materials provided with the distribution.
.\" 3. All advertising materials mentioning features or use of this software
.\"    must display the following acknowledgement:
.\"	This product includes software developed by Angelos D. Keromytis.
.\" 4. The name of the author may not be used to endorse or promote products
.\"    derived from this software without specific prior written permission.
.\"
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.\" $FreeBSD$
.\"
.Dd June 16, 2006
.Dt ENC 4
.Os
.Sh NAME
.Nm enc
.Nd Encapsulating Interface
.Sh SYNOPSIS
To compile this driver into the kernel,
place the following line in your
kernel configuration file:
.Bd -ragged -offset indent
.Cd "device enc"
.Ed
.Sh DESCRIPTION
The
.Nm
interface is a software loopback mechanism that allows hosts or
firewalls to filter
.Xr fast_ipsec 4
traffic using any firewall package that hooks in via the
.Xr pfil 9
framework.
.Pp
The
.Nm
interface allows an administrator
to see outgoing packets before they have been processed by
.Xr fast_ipsec 4 ,
or incoming packets after they have been similarly processed, via
.Xr tcpdump 8 .
.Pp
The
.Dq Li enc0
interface inherits all IPsec traffic.
Thus all IPsec traffic can be filtered based on
.Dq Li enc0 ,
and all IPsec traffic could be seen by invoking
.Xr tcpdump 8
on the
.Dq Li enc0
interface.
.Sh EXAMPLES
To see all outgoing packets before they have been processed via
.Xr fast_ipsec 4 ,
or all incoming packets after they have been similarly processed:
.Pp
.Dl "tcpdump -i enc0"
.Sh SEE ALSO
.Xr tcpdump 1 ,
.Xr bpf 4 ,
.Xr fast_ipsec 4 ,
.Xr ipf 4 ,
.Xr ipfw 4 ,
.Xr pf 4